Method of regenerating used lubricating oil



United States Patent 0 3,417,012 METHOD OF REGENERATING USED LUBRICATING OIL Mario Morace, Via Freguglia 2, Milan, Italy N0 Drawing. Filed Nov. 14, 1966, Ser. No. 593,631 1 Claim. (Cl. 208181) ABSTRACT OF THE DISCLOSURE Method of regenerating used lubricating oil, including the steps of adding to a used lubricating oil water containing sulphuric acid, zinc chloride and if desired a compound such as perborate, persulphate and permanganate, heating the mixture while stirring initially at atmospheric pressure and then under vacuum, increasing the vacuum and the temperature up to limits required by the desired characteristics of the finished product, cooling down the mixture and leaving it to settle for decantation.

This invention relates to a method of regenerating used, exhausted, aged or deteriorated lubricating oils so as to restore them to a condition in which they have substantially the same lubricating characteristics as in their original form. The invention further relates to lubricating oils regenerated according to this method.

It is known that the mineral lubricating oils, mainly but not exclusively used for lubricating purposes, after a certain period and in dependence on the conditions of working and use, are partially exhausted, fouled, altered or deteriorated so that they must be replaced. The ever increasing consumption of lubricating oils, a direct consequence of industrial development, has long since resulted in the development and application of so-called regenerating, purification or re-refining methods serving the purpose of restoring to the used, exhausted or deteriorated oil characteristics permitting to use it again for lubricating purposes. These methods generally comprise a process of refining the used, exhausted or deteriorated lubricating oil.

It is also known'that the previously known methods of regenerating lubricating oils have certain disadvantages and generally provide small yields from the treated oil in respect of quantities and in part also in respect of quality, that is to say that the ratio between the quantity of the used oil treated and the quantity of the regenerated useful oil is disadvantageous.

The regenerating methods for used, exhausted or deteriorated oil can only in part be compared with the methods of refining the original distilled lubricants. In fact, with the latter it is only necessary to remove certain undesired components such as resinous substances and components with a low viscosity index and chemically unstable components: components that can be easily located and the removal of which can be determined in advance. In re-refining used or exhausted oil it is however necessary to remove numerous very different and unpredictable components since the used lubricating oil, apart from the substances deteriorated by use, contains numerous additives and foreign substances.

Thus, although it is known that the use of sulphuric acid in refining the original distilled lubricants has long since and practically completely been replaced by selectively acting solvents which remove the previously ascertained undesired components by physical separating processes, their use cannot be extended with satisfactory results also to the field of used lubricating oils since the selective action of these solvents cannot be utilized completely with used lubricating oils. Due to these circumstances and also on account of the high costs of the very 3,417,012 Patented Dec. 17, 1968 delicate equipment, the use of solvents in the regeneration of used lubricating oils is not advisable from the economical point of view.

Therefore, the known methods of regenerating used lubricating oils are mostly restricted to the use of sul- .phuric acid, though in most cases with the addition of other substances and in various forms of application, providing a combined physical and chemical effect for removing the most various undesired components and foreign substances. It is known that the effects of the sulphuric acid are rather complicated and not yet completely known. In fact, it acts as an oxidant and polymerizer and leads to the formation of macromolecules appearing in a non-crystalline and impure state as well as in combination with oil and unreacted acid. However, the foreign substances and undesired components can only be separated from the mass of the lubricating oil by precipitation or centrifugation, leaving considerable quantities of oil sludge. Further, since the sulphuric acid acts upon the scission products of the additives present in the original lubricating oil, it results in the formation of malodorous secondary products having a disadvantageous effect when not eliminated.

Apart from the poor economic efficiency of the regenerating methods using sulphuric acid, due mainly to the large amount of oil reduced to useless sludge, these methods have numerous technical disadvantages. For example, the exhausted oil must first be dehydrated to maintain, on the one hand, the acid concentration necessary to ensure its efficiency and to avoid, on the other hand, that the heat development occurring during the reaction between acid and water might impair the effect of the sulphuric acid. The heating to which the oil is subjected during the dehydrating process reduces the quality of the oil in that the intensity of its colouring is increased and the number of the oxidation products is also increased, which, as is known, leads to chain reactions. Further, the use of sulphuric acid results in a decrease of important characteristics of the lubricating oil because of the uncontrollable conditions under which the treatment is carried out and which produce a disadvantageous effect of the acid on the polar components and on the turbidity and solidification inhibitors.

Finally, also the disadvantages are known which are due to the very nature of the sulphuric acid, especially its dangerousness and the difiiculties encountered in its transportation and in the destruction of the residual acid sludge.

It is therefore an object of the present invention to provide a method of regenerating and/or re-refining used, exhausted or deteriorated lubricating oils, in which the aforementioned technical disadvantages are removed or at least considerably reduced, and the ratio between the exhausted and regenerated lubricant is improved and thus the economical usefulness of the method for industrial purposes is increased.

A further object of the present invention is the production of regenerated lubricating oils having a quality not inferior to that of the original lubricating oils, especially with respect to stability and viscosity characteristics.

To achieve these objects, the invention provides a method of regenerating used lubricating oils, which is characterized in that the used lubricating oil is brought into contact, in an acidulated environment, with a halogen derivate and a monatomic oxygen produced in situ, and the mixture is heated while stirring initially at atmospheric pressure and then under vacuum while the vacuum and the temperature are increased up to the limits required by the desired characteristics of the finished product.

The conditions of treatment, i.e., the heating with stirring first at atmospheric pressure up to 230266 F. and then under gradually increasing vacuum, constitute a particular basic feature of the present invention in that they permit, on the one hand, the exercise of the desulphurizing, decolouring, deodorizing, polymerizing, saturating, precipitating and catalyzing functions of the halogen derivate and, on the other hand, prevent the occurrence of effects which would jeopardize the results of the treatment, such as that of cracking and dehydrogenation and cycling. The monatomic oxygen produced in situ within the mass of the used lubricating oil, through its oxidizing and polymerizing effect, results and participates in the conversion of the undesired components and foreign substances, which originally were in the form of colloidal molecules, into crystalline macromolecules which can be removed by mechanical processes. Moreover, the process of oxidation performed by the monatomic oxygen in practice is continued up to the final stage of the oxidation reaction to provide a regenerated product having high stability characteristics or resistance to oxidation.

To ensure an efficient execution of the reactions, a certain minimum amount of water is necessary which is about 0.5 of the mass of oil to be regenerated. To permit the elimination of the preparatory analysing operations necessary to ascertain the quantity of water originally present in the exhausted oil, water may be added, prior to the introduction of the salts, that has been acidulated by adding mineral acids at a ratio of 20-25% of the water, selecting the amount of water to be added so as to be sufiicient to ensure a surplus of the amount of water required. The surplus of water does not disturb or impair the effective execution of the reactions.

The various reactions and the regrouping process of the carbon particles and other suspended foreign substances are terminated within a relatively short period of time. The continuation of the treatment under vacuum and at a higher temperature ensures the undisturbed performance of the reactions produced by the halogen derivative and the removal of the last traces of the gaseous reaction products and of the water present and completes the polymerisation of any naphthenes that may be present and finally, if it is desired at this stage, permits the desired flash point of the finished product to be obtained.

The particles and foreign substances, which as mentioned above have been converted into a substantially crystalline form, can be removed by mechanical means such as by filtering, centrifuging or the like, but also i by decanting. Consequently, the execution of any distillation treatment known per se, with or without the addition of earth, is greatly facilitated and can be carried out with particular advantages if the product regenerated as described above is treated with sulphuric acid in the various treatment phases performed in the course of the regeneration process. The distillation process is then carried out on clear products free from water, foreign substances and acids and can be continued until practically all of the product has been distilled, providing the possibility of collecting the various viscosity grades.

Metal chlorides, preferably zinc chloride, are used as the halogen derivatives. As the inorganic acid salts, capable of developing monatomic oxygen in the presence of water, the perborates, persulphates and permanganates of sodium and/or potassium and their analogues are used.

The quantitative yield of the method proposed by the invention can be estimated by the fact that the loss of useful oil fractions ascertained in the mechanical treatment or during the decanting of the oil subjected to the method of the invention, is limited to a very low percentage. By way of comparison, reference is made to the losses occurring in the known sulphuric acid treatment in which the impurities appear in the form of colloidal solutions and sometimes even colloidal emulsions and in which the precipitating effect of the sulphuric acid re sults in the elimination of considerable quantities of useful oil.

Hereinafter some examples of experiments carried out are given.

EXAMPLE 1 To 1000 grams of used lubricating oil as collected and having a water content of 0.7% there were added 5 grams of water previously mixed with 25% of sulphuric acid and 10 grams of commercial zinc chloride at 150.8 P. Then the mixture was heated to 266 F. while stir ring. With continued stirring, heating was increased to 536 F. under vacuum and the vacuum gradually increased from 30 to 65 mm. After having been slightly cooled down to 320 F., the oil was left for 24 hours to settle for decantation. The decanted product was treated with 6% of activated decolouring earth and filtered. 815 grams of clear lubricating oil with a flash point of 419 F., 94 grams of light products, and 82 grams of sludge were obtained.

EXAMPLE 2 1000 grams of used lubricating oil with the same characteristics as that in Example 1 was treated in the same way as in Example 1 but with a further addition of 2 grams of commercial soda perborate. By filtering with decolouring earth after a settling period of 12 hours, 840 grams of clear lubricating oil with a flash point of 413=6 F., 97 grams of light products, and 52 grams of residual sludge were obtained.

EXAMPLE 3 1000 grams of used lubricating oil of the same characteristics as in Example 1 and treated as in Example 2, after having been heated under vacuum up to 536 F., was filtered initially on a bed of natural earth and then with 5% of activated decolouring earth. The yield was 865 grams of lubricating oil, 92 grams of light products, and 3234 grams of sludge retained by the filter bed.

EXAMPLE 4 1000 grams of used lubricating oil of the same characteristics as in Example 1 was treated according to the method of Example 2. Heating under vacuum was interrupted at 482 F. and the mixture was filtered on a bed of natural earth. After 3% of activated decolouring earth had been added to the filtered product, it was distilled under vacuum and yielded four fractions providing a total of 962 grams of products of different viscosity.

What I claim is:

1. A method of regenerating used lubricating oil, C0111- prising the steps of adding to an ordinary used lubricating oil water containing 25% sulphuric acid at a ratio of at least 0.5% by weight of the used lubricating oil, zinc chloride at a ratio of at least 0.1% by weight of the used lubricating oil, and a compound selected from the group consisting of perborate, persulphate and permanganate, heating the mixture while stirring initially at atmospheric pressure and then under vacuum, increasing the vacuum and the temperature up to limits required by the desired characteristics of the finished product, cooling down the mixture and leaving it to settle for decantation.

References Cited UNITED STATES PATENTS 1,842,983 1/1932 Hanke 208181 DELBERT E. GANTZ, Primary Examiner.

H. LEVINE, Assistant Examiner.

U.S. Cl. X.R. 208184 

